Buildings have fireproof compartments defined depending on the types and specifications of the buildings. In the fireproof compartments, according to the specifications, flooring materials and wall materials for fireproof construction or semi-fireproof construction prescribed by the Building Standards Act are used. The flooring materials and the wall materials for fireproof construction or semi-fireproof construction prescribed by the Building Standards Act are those defined by the Minister of Land, Infrastructure, Transport and Tourism or certified by the Minister of Land, Infrastructure, Transport and Tourism, and examples thereof include ferroconcrete; concrete blocks, brick constructions, and stone constructions that are reinforced with iron materials; iron materials covered with steel mortar or concrete on both surfaces thereof; lightweight foamed concrete; precast concrete plates; and laminates of plywood and gypsum board, hard wood chip cement board, or lightweight foamed concrete.
Incidentally, buildings are provided with piping (such as electrical conduits, drain pipes, and ducts). Such piping passes through the above-mentioned fireproof compartment in some cases.
When a through-hole through which piping or the like passes (hereinafter, referred to as “compartment pass-through portion”) is provided to the above-mentioned fireproof compartment, occurrence of fire may cause a big fire accident within a short period of time by that the fire and smoke quickly penetrate from the room where the fire occurred to the next room having the fireproof compartment therebetween through the compartment pass-through portion.
Therefore, the Building Standards Act establishes that only materials that passed a fire-resistant test for compartment pass-through and certified by the Minister of Land, Infrastructure, Transport and Tourism or evaluated by fire defense can be used as the piping material passing through the compartment pass-through portion in a building.
Therefore, the compartment pass-through portion is provided with fire-protection measures for caulking a gap with a noncombustible material such as mortar after installing the piping passing through the compartment so that no gap is formed between the compartment pass-through portion and the piping.
When the piping material is a metal, since the piping material itself is heat resistant and noncombustible, a sufficient effect is observed only by caulking the gap with a noncombustible material such as mortar, as described above. However, the metal piping has a large weight and therefore has a problem that the workability in transferring and in construction is inferior.
On the other hand, when the piping material is a synthetic resin, the piping is light in weight, excellent in workability, and easy to bond, compared to the metal piping. The synthetic resin piping has thus various merits, but is inferior in heat resistance and fire resistance. Therefore, in fire, the piping material is lost by burning or is deformed by the heat to generate a gap between the compartment pass-through portion and the piping material, which may allow the heat, fire, and smoke occurred at one side of the fireproof compartment to reach the other side.
Accordingly, for example, it is employed fire-protection measures in which a sheet-like covering material having fire-resistance and expansibility is wound on the outer surface of the synthetic resin piping material. As the fire-resistant resin composition constituting the sheet-like covering material, proposed are those in which a vinyl chloride-based resin is blended with heat-expandable graphite, an inorganic filler, and a plasticizer and also blended with a specific phosphorus compound (for example, refer to Patent Document 1) and those in which a base resin, such as rubber, a thermoplastic elastomer, or a liquid polymer, is blended with heat-expandable graphite serving as an inorganic expansion agent and also blended with a resin serving as a deformation-preventing resin, such as a polycarbonate resin or a polyphenylene sulfide resin (for example, refer to Patent Document 2).
However, in the fire-protection measures using the sheet-like covering material, a synthetic resin piping material is temporarily installed, and then the sheet-like covering material is wound to the piping material at a portion previously determined. Subsequently, the piping material is supported and fixed, and then the opening is filled back with mortar. Therefore, the measures has a large number of work units and takes a long time and also has a problem that the adjustment of the piping position after the winding of the sheet-like covering material to the piping material is difficult.
Accordingly, the above-mentioned problems can be solved by directly producing a piping material with a resin composition having fire-resistance and expansibility, but since the fire-resistant resin composition in Patent Document 1 contains large amounts of an inorganic filler and a plasticizer in a vinyl chloride-based resin, the piping material formed therewith cannot obtain a high mechanical strength that is an indispensable requirement in a pipe. Furthermore, since the fire-resistant resin composition in Patent Document 2 contains rubber, a thermoplastic elastomer, or a liquid polymer as the base resin, the piping material formed therewith cannot obtain a high mechanical strength that is an indispensable requirement in a pipe, as in the fire-resistant resin composition of Patent Document 1.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2006-348228    [Patent Document 2] Japanese Patent No. 3133683